Working of SU Carburetor:
When the accelerator is operated, the piston moves up and down in the throat controlling the supply of air, and the needle moves up and down to the jet controlling to the supply of fuel.
When the piston moves up, throat area increases, for more air passes through it. The needle also moves up increasing the annular area in the jet to pass more fuel.
When the piston moves down,
The piston tapered needle is so designed that they maintain the correct air-fuel mixture at the different operating condition of the engine. By changing the tapered needle and adopting a suitable one, the same
- The upper side of the piston is connected to the throttle passage through a slot cut in the piston.
- The lower side
the exposedto the atmospheric pressure.
Thus, the piston at any instant depends upon the balance of its own weight (downward) against the vacuum force (upward). As the load of the piston is constant the vacuum also remains constant.
The jet can be moved up and down about to the tapered needle, by an adjusting screw fitted at the bottom of the screw. This is done for adjusting the mixture strength. There is to separate idling or slow speed system and on accelerating pump
Types of SU Carburetor
SU carburettors were provided in several “throat sizes” in both inch and millimetre measurement. These
“H” types have float bowl with an arm cast into its base. It is mounted to the bottom of the
“HD” it has the float bowl with its arm fastening directly below, and concentric with the jet. The arm has a flange that tightened with four screws at the bottom of
“HS” The main body is covered with rubber, fuel is supplied by an external pipe to the jet.
“HIF” It has horizontal Integral Float.
“HV”, “OM” and “KIF” types less commonly used.
Advantages and Uses
The main advantage of SU
SU Carburetors were widely used in automobile vehicles from much of the twentieth century. These are also used in aircraft engines including the early versions of the Rolls Royce.
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